feat(iterable_differ): support immutable lists

Closes #7127

modules/angular2/src/core/change_detection/differs/default_iterable_differ.ts

@@ -109,7 +109,6 @@ export class DefaultIterableDiffer implements IterableDiffer {
 
   onDestroy() {}
 
-  // todo(vicb): optim for UnmodifiableListView (frozen arrays)
   check(collection: any): boolean {
     this._reset();
 
@@ -119,24 +118,27 @@ export class DefaultIterableDiffer implements IterableDiffer {
     var item;
     var itemTrackBy;
     if (isArray(collection)) {
-      var list = collection;
-      this._length = collection.length;
+      if (collection !== this._collection || !ListWrapper.isImmutable(collection)) {
+        var list = collection;
+        this._length = collection.length;
 
-      for (index = 0; index < this._length; index++) {
-        item = list[index];
-        itemTrackBy = this._trackByFn(index, item);
-        if (record === null || !looseIdentical(record.trackById, itemTrackBy)) {
-          record = this._mismatch(record, item, itemTrackBy, index);
-          mayBeDirty = true;
-        } else {
-          if (mayBeDirty) {
-            // TODO(misko): can we limit this to duplicates only?
-            record = this._verifyReinsertion(record, item, itemTrackBy, index);
+        for (index = 0; index < this._length; index++) {
+          item = list[index];
+          itemTrackBy = this._trackByFn(index, item);
+          if (record === null || !looseIdentical(record.trackById, itemTrackBy)) {
+            record = this._mismatch(record, item, itemTrackBy, index);
+            mayBeDirty = true;
+          } else {
+            if (mayBeDirty) {
+              // TODO(misko): can we limit this to duplicates only?
+              record = this._verifyReinsertion(record, item, itemTrackBy, index);
+            }
+            if (!looseIdentical(record.item, item)) this._addIdentityChange(record, item);
           }
-          if (!looseIdentical(record.item, item)) this._addIdentityChange(record, item);
-        }
 
-        record = record._next;
+          record = record._next;
+        }
+        this._truncate(record);
       }
     } else {
       index = 0;
@@ -156,9 +158,9 @@ export class DefaultIterableDiffer implements IterableDiffer {
         index++;
       });
       this._length = index;
+      this._truncate(record);
     }
 
-    this._truncate(record);
     this._collection = collection;
     return this.isDirty;
   }

modules/angular2/src/facade/collection.dart

@@ -1,6 +1,6 @@
 library facade.collection;
 
-import 'dart:collection' show IterableBase;
+import 'dart:collection' show IterableBase, UnmodifiableListView;
 import 'dart:convert' show JsonEncoder;
 export 'dart:core' show Iterator, Map, List, Set;
 import 'dart:math' show max, min;
@@ -106,6 +106,9 @@ class ListWrapper {
   static List createFixedSize(int size) => new List(size);
   static List createGrowableSize(int size) =>
       new List.generate(size, (_) => null, growable: true);
+  static UnmodifiableListView createImmutable(List input) {
+    return new UnmodifiableListView(input);
+  }
 
   static bool contains(List m, k) => m.contains(k);
   static int indexOf(List list, value, [int startIndex = 0]) =>
@@ -221,6 +224,10 @@ class ListWrapper {
     }
     return solution;
   }
+
+  static bool isImmutable(List l) {
+    return l is UnmodifiableListView;
+  }
 }
 
 bool isListLikeIterable(obj) => obj is Iterable;

modules/angular2/src/facade/collection.ts

@@ -178,6 +178,11 @@ export class ListWrapper {
   static createFixedSize(size: number): any[] { return new Array(size); }
   static createGrowableSize(size: number): any[] { return new Array(size); }
   static clone<T>(array: T[]): T[] { return array.slice(0); }
+  static createImmutable<T>(array: T[]): T[] {
+    var result = ListWrapper.clone(array);
+    Object.seal(result);
+    return result;
+  }
   static forEachWithIndex<T>(array: T[], fn: (t: T, n: number) => void) {
     for (var i = 0; i < array.length; i++) {
       fn(array[i], i);
@@ -265,6 +270,8 @@ export class ListWrapper {
     }
     return solution;
   }
+
+  static isImmutable(list: any[]): boolean { return Object.isSealed(list); }
 }
 
 export function isListLikeIterable(obj: any): boolean {

modules/angular2/test/core/change_detection/differs/default_iterable_differ_spec.ts

@@ -31,7 +31,6 @@ class ComplexItem {
   toString() { return `{id: ${this.id}, color: ${this.color}}` }
 }
 
-// todo(vicb): UnmodifiableListView / frozen object when implemented
 export function main() {
   describe('iterable differ', function() {
     describe('DefaultIterableDiffer', function() {
@@ -314,6 +313,36 @@ export function main() {
             }));
       });
 
+      it('should not diff immutable collections if they are the same', () => {
+        // Note: Use trackBy to know if diffing happened
+        var trackByCount = 0;
+        var trackBy = (index: number, item: any): any => {
+          trackByCount++;
+          return item;
+        };
+        var differ = new DefaultIterableDiffer(trackBy);
+        var l1 = ListWrapper.createImmutable([1]);
+
+        differ.check(l1);
+        expect(trackByCount).toBe(1);
+        expect(differ.toString())
+            .toEqual(
+                iterableChangesAsString({collection: ['1[null->0]'], additions: ['1[null->0]']}));
+
+
+        trackByCount = 0;
+        differ.check(l1);
+        expect(trackByCount).toBe(0);
+        expect(differ.toString())
+            .toEqual(iterableChangesAsString({collection: ['1'], previous: ['1']}));
+
+        trackByCount = 0;
+        differ.check(l1);
+        expect(trackByCount).toBe(0);
+        expect(differ.toString())
+            .toEqual(iterableChangesAsString({collection: ['1'], previous: ['1']}));
+      });
+
       describe('diff', () => {
         it('should return self when there is a change',
            () => { expect(differ.diff(['a', 'b'])).toBe(differ); });